Queen's duty-bound to practice (8)
I believe the answer is:
exercise
'to practice' is the definition.
(synonyms)
'queen's duty-bound' is the wordplay.
I cannot really see how this works, but
'queen' could be 'er' (abbreviation for Elizabeth Regina) and 'er' is present in the answer.
'duty' could be 'excise' (both can mean a tax) and 'excise' is present in the remaining letters.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for exercise that I've seen before include "Gym activity?" , "Exertion to develop fitness" , "Task for pupil" , "Employment" , "Practice session" .)